Emulsions, dispersions or solutions containing macromolecular substances have heretofore been used for imparting dustproof properties to asbestos articles. According to conventional techniques, such treating agents are impregnated into the interior substrate and/or onto the surface portions of an asbestos article and then the dispersion medium or solvent is removed by drying, thereby leaving a film of the macromolecular substance contained in the treating agent. Since in the secondary processing of asbestos articles they are subjected to cutting and other processing operations, it is essential that the dustproof properties be imparted uniformly to not only the surface portions but also the interior substrate of asbestos articles. However, in conventional techniques, the dispersed substance or solute tends to gather on the surface portions of an asbestos article at the drying step, thus the distribution density is frequently lower in the interior substrate portion of the article. Consequently, optimal dustproof effects cannot be obtained using conventional techniques.